Re: [PATCH v3 03/12] iommu: Add new flag to explictly request PASID capable domain

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2024/10/18 20:43, Jason Gunthorpe wrote:
> On Fri, Oct 18, 2024 at 11:43:02AM +0800, Baolu Lu wrote:
>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>> index 9f6b0780f2ef..d7546ab18e18 100644
>> --- a/drivers/iommu/intel/iommu.c
>> +++ b/drivers/iommu/intel/iommu.c
>> @@ -3539,12 +3539,16 @@ intel_iommu_domain_alloc_user(struct device *dev,
>> u32 flags,
>>          }
>>
>>          if (flags &
>> -           (~(IOMMU_HWPT_ALLOC_NEST_PARENT |
>> IOMMU_HWPT_ALLOC_DIRTY_TRACKING)))
>> +           (~(IOMMU_HWPT_ALLOC_NEST_PARENT |
>> +              IOMMU_HWPT_ALLOC_DIRTY_TRACKING) |
>> +              IOMMU_HWPT_ALLOC_PASID))
>>                  return ERR_PTR(-EOPNOTSUPP);
>>          if (nested_parent && !nested_supported(iommu))
>>                  return ERR_PTR(-EOPNOTSUPP);
>>          if (user_data || (dirty_tracking && !ssads_supported(iommu)))
>>                  return ERR_PTR(-EOPNOTSUPP);
>> +       if ((flags & IOMMU_HWPT_ALLOC_PASID) && !pasid_supported(iommu))
>> +               return ERR_PTR(-EOPNOTSUPP);
> I think the decision here should only be about supported domain
> type. Like on AMD if the iommu instance doesn't support v2 then it
> should fail.
> 
> If there is some other thing that says the instance supports pasid,
> that should be checked during attach time only.
> 
> IIRC intel can use either page table format for pasid, so it probably
> doesn't need to do anything here?

yes.

Thanks,
baolu